This application is based on Patent Application No. 10-376678 (1998) filed Dec. 25, 1998 in Japan, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to an ink printing method and an ink printing apparatus, and more particularly to an ink printing method and apparatus which perform printing by using a processing liquid insolubilizing a colorant in an ink. The ink printing method and apparatus of the present invention are applicable to equipment such as a printer, a copy machine, a facsimile machine or the like, that prints letters, images or the like on a printing medium such as paper or the like, and also applies to a printing mechanism of such equipment.
2. Description of the Prior Art
To improve density and fixability of a printed image has been an important focus in the ink-printing field. More specifically, ink printing has been required to provide printing density and fixation speed as high as those associated with electrophotography, which is another technique for printing. Under these circumstances, the above described problems are more complex in printing full-color images than in printing only black letters or monochromic images with a black ink.
Full-color printing uses relatively highly penetrative inks, e.g., cyan (C), magenta (M) and yellow (Y) inks, as one of the methods to prevent these color inks from running into each other at boundaries between them. This method prevents each of the inks from running along a printing medium surface. However, use of the highly penetrative ink may cause other types of problems, such as difficulty in securing the high density or optical density (hereinafter referred to as OD), resulting from accelerated penetration of a dye colorant in the ink deep into the printing medium. Penetration of the dye colorant deep into the medium may degrade properties related to strike-through OD, when the printing medium (e.g., common paper) is sufficiently thin. Strike-through OD is an OD value of the printed matter when it is viewed from a back side of the printing medium, where the property related to the strike-through OD is better when the OD value is lower.
In the same way as described above, running of a black (Bk) ink at the boundary with a color ink can be also solved by increasing its penetrability. However, a character (e.g., a letter) printed with a penetrative Bk ink may have unsatisfactory print quality with respect to OD and sharpness at an edge of the letter. Use of a Bk ink of lower penetrability for improving the above described character quality in preference to other print quality may cause problems, such as running of the Bk ink at the interface with a color ink and slow fixation.
One of methods for solving these problems related to OD and fixation is a method using a heating mechanism. However, this method requires a heating source, e.g., heater, that consumes much electric power and causes problems, e.g., increased cost.
The assignee of the present invention has variously proposed to use a processing liquid which insolubilizes colorants in inks for improving waterproofness, OD, and fixability of a printed matter.
However, no ink printing method developed so far gives high OD both for characters/monochromic images with a Bk ink and full-color images, while still allowing high-speed fixation of ink.
An object of the present invention is to provide an ink printing method and an ink printing apparatus which give high OD both for monochromic and color images and still allows high-speed fixation.
Another object of the present invention is to provide an ink printing method and an ink printing apparatus which reduces strike-through to a back side of a printing medium.
In a first aspect of the present invention, there is provided an ink printing method using at least three types of liquid droplets, comprising the steps of:
causing a first ink droplet containing a first colorant and a processing liquid droplet, which works to accelerate solidification of the first colorant, to mix and react with each other on the printing medium to form a secondary liquid that contains a non-ionic surfactant at a concentration below its critical micelle concentration (CMC) in water; and
applying a second ink droplet onto the secondary liquid, the second ink droplet containing a second colorant and a non-ionic surfactant having a concentration of its CMC in water, or more.
In a second aspect of the present invention, there is provided an ink printing method using at least three types of liquid droplets, comprising the steps of:
causing a first ink droplet containing a first colorant and a processing liquid droplet, which works to accelerate solidification of the first colorant, to mix and react with each other on the printing medium to form a secondary liquid that has a Ka value below 5; and
applying a second ink droplet onto the secondary liquid, the second ink droplet containing a second colorant and a non-ionic surfactant having a concentration of its CMC in water, or more.
In a third aspect of the present invention, there is provided an ink printing apparatus which uses a head ejecting at least three types of liquid droplets and ejects the liquid droplet from the head onto a printing medium to perform printing, the apparatus comprising:
first applying means for controlling ejection of the liquid from the head so as to cause a first ink droplet containing a first colorant and a processing liquid droplet, which works to accelerate solidification of the first colorant, to mix and react with each other on the printing medium to form a secondary liquid that contains a non-ionic surfactant having a concentration below its critical micelle concentration (CMC) in water; and
second applying means for controlling ejection of the liquid from the head to apply a second ink droplet onto the secondary liquid, the second ink droplet containing a second colorant and a non-ionic surfactant having a concentration of its CMC of water, or more.
In a fourth aspect of the present invention, there is provided an ink printing apparatus which uses a head ejecting at least three types of liquid droplets and ejects the liquid droplet from the head onto a printing medium to perform printing, the apparatus comprising:
first applying means for controlling ejection of the liquid from the head so as to cause a first ink droplet, containing a first colorant and a processing liquid droplet which works to accelerate solidification of the first colorant, to mix and react with each other on the printing medium to form a secondary liquid that has a Ka value below 5; and
second applying means for applying a second ink droplet onto the secondary liquid, the second ink droplet containing a second colorant and a non-ionic surfactant at a concentration of its CMC in water, or more.
According to the configuration described above, after the first ink droplet containing the first colorant and the processing liquid droplet are mixed to react on the printing medium to form the secondary liquid, the second ink droplet of high penetrability containing the second colorant is applied onto the secondary liquid. Thereby, the first colorant can be accelaratory (i.e., quickly) solidified on the surface of the printing medium in the presence of the processing liquid droplet and the first colorant becomes a large block, at the molecular level, on the printing medium. Since the second ink droplet of high penetrability is applied onto the block, an aqueous solvent for the ink can penetrate quickly, while leaving the colorant on the printing medium surface.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.